Been a while since I've been around. My 98 2500 CTD with 235k miles has been running well...until recently. Suddenly it's way down on power. Way down. I'd been meaning to install a gauge cluster in preparation to turning up the boost a bit. Now that it's down on power, I installed a mechanical boost gauge. Here's what I'm dealing with:

• 0 psi boost at idle.
  
• 7 psi boost at wide open throttle
  
• No black smoke
  
• Engine runs very smoothly, just no power
  
• No hard starting
  
• Pinched off the line to the wastegate temporarily, no change to boost numbers.
  
• Built a pressure tester and confirmed that the boost lines and intercooler hold 25 psi with no leaks

.
I still have the stock fuel pump and was not planning to install a fuel pressure gauge since it's a 12V.

I'm thinking the engine itself is healthy. Burns no oil and runs very smoothly. Based on what I've read, I'm thinking that I have a turbo problem, a wastegate problem or a fueling problem. Since pinching the wastegate line does not change the boost, wouldn't that point to a wastegate problem? Also, if my fuel system was functioning correctly, I thought I should have lots of black smoke if my boost is down. However, most folks who have fuel problems seem to have rough running too. My 12V is still very smooth.

If anyone has any ideas about where to start, I'd really appreciate it.

Thanks...Boatman1

 

Check the line from the head to the AFC housing on the injection pump. This line needs to be fully intact and free of obstructions. If it is broken, pinched, or clogged then your injection pump doesn’t have a boost signal. This impacts fueling which would impact everything.

That’s a possibility. There are dozens others. But it’s the first that I would check based on what’s been said.

What work has been done to the truck so far?

 

Crawler - Thanks for the reply. Will check that line first. No mods on the truck yet. Owned if for about 7 years and put 35K miles on it. Taken care of lots of maintenance items though. Will let you know what I find.

Bioatman1

 

It's been literally a year since I had a low power condition on my 98 12V. I checked just about everything and got so disgusted, I just let it sit until after new years. Turned out to be low fuel pressure. I removed the bleed screw (bolt) from the top of the fuel filter cannister, found a long metric bolt to fit, cut the head off, drilled through the center, chucked it in a drill, turned the threads on the top into barbs, clamped on a 4 ft. hose to a fuel pressure gauge taped on the dash and went for a ride. Fuel pressure at idle was 5 psi. At WOT, fuel pressure quickly dropped to 0. Problem found. After installing a new Cummins fuel pump from Geno's, fuel pressure at idle is 25 psi and at WOT is 30 psi. Truck now shows 19 psi boost at WOT. Runs just fine. It surprised me how smoothly the truck ran as it was running out of fuel with the worn out pump. I figured if it was running out of fuel, it should run choppy. Not so.

While I was at it, I caught up on some overdue maintenance. I killed the KDP, replaced the front main seal, put in a new Cummins thermostat, new power steering pump and resealed the vacuum pump.

Once that was all done, I finally got to the body. The truck was very clean, but ruety on the normal spots. Replaced a lot of sheet metal panels:
- New door skin bottoms and inner bottoms (all 4)
- New inner and outer rockers
- New front fender bottoms
- New front body mounts.

Took a while, but this thing is now rust free, and well prepped (Pettit RustLok). When I get it out of the driveway, it'll get a liberal bath of Fluid Film.

The only real problem I had was that each of the each of the original door skins warped a little when I welded them, even though I went slowly and used a skip pattern and flanged the replacement panel seems. Those original door skins sure are thin.

One thing I came up with, that I haven't seen described before was a way to get the fuel filter cannister filled after installing a new filter. Guidance I've seen is to press the manual plunger on the mechanical pump until your hand goes numb. Instead, I used the barb I machined to test fuel pressure and hooked it up to a MityVac pump I use for brake bleeding. By pulling a vacuum on the fuel canniser, I primed it in 15 seconds, installed the original bleed screw and it fired right up. Might save you some time.

Take care...Boatman1